lkml.org 
[lkml]   [2016]   [Mar]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH] usb: gadget: f_midi: Fixed a bug when buflen was smaller than wMaxPacketSize
Date
On Wed, Mar 09 2016, Felipe F. Tonello wrote:
> buflen by default (256) is smaller than wMaxPacketSize (512) in high-speed
> devices.
>
> That caused the OUT endpoint to freeze if the host send any data packet of
> length greater than 256 bytes.
>
> This is an example dump of what happended on that enpoint:
> HOST: [DATA][Length=260][...]
> DEVICE: [NAK]
> HOST: [PING]
> DEVICE: [NAK]
> HOST: [PING]
> DEVICE: [NAK]
> ...
> HOST: [PING]
> DEVICE: [NAK]
>
> This patch fixes this problem by setting the minimum usb_request's buffer size
> for the OUT endpoint as its wMaxPacketSize.
>
> Signed-off-by: Felipe F. Tonello <eu@felipetonello.com>

Acked-by: Michal Nazarewicz <mina86@mina86.com>

But see comment below:

> ---
> drivers/usb/gadget/function/f_midi.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
> index 8475e3dc82d4..826ba641f29d 100644
> --- a/drivers/usb/gadget/function/f_midi.c
> +++ b/drivers/usb/gadget/function/f_midi.c
> @@ -366,7 +366,9 @@ static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
> /* allocate a bunch of read buffers and queue them all at once. */
> for (i = 0; i < midi->qlen && err == 0; i++) {
> struct usb_request *req =
> - midi_alloc_ep_req(midi->out_ep, midi->buflen);
> + midi_alloc_ep_req(midi->out_ep,
> + max_t(unsigned, midi->buflen,
> + bulk_out_desc.wMaxPacketSize));

Or, just:

+ midi_alloc_ep_req(midi->out_ep,
+ bulk_out_desc.wMaxPacketSize);

Packet cannot be greater than wMaxPacketSize so there is no need to
allocate more (if buflen > wMaxPacketSize).

> if (req == NULL)
> return -ENOMEM;
>

I’m also wondering whether it would be beneficial to get rid of buflen
all together and use wMaxPacketSie for in endpoints as well? Is that
feasible?

--
Best regards
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»

\
 
 \ /
  Last update: 2016-03-12 00:41    [W:0.153 / U:0.024 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site